Growth hormone is important in producing normal growth in children, but the means by which it does so are not known. It may be that several forms of growth hormone are produced, but not all the forms can be recognized in the tests presently used to measure the blood content of growth hormone. This research will determine whether the forms of growth hormone change with nutritional changes at puberty by measuring blood concentrations of growth hormone using a new biological assay. The effect of weight loss to increase growth hormone concentration and biological activity will also be studied. Baseline hormone studies will be performed where blood is obtained through an indwelling catheter every 15 minutes for 24 hours. Then a 12 week intervention will be given by a psychologist and nutritionist to promote weight loss. Following the intervention, blood will again be obtained for 24 hours. These studies may have practical applications for improving growth in children, since new categories for growth failure may be defined. If growth hormone forms with enhanced biological potency can be determined, we may be able to design new drugs to produce better growth. We may be able to better understand the role of growth hormone in metabolism.